That's how one senator's off-the-cuff remark that Hurricane Katrina would cost the federal government $200 billion became the de facto estimate.

I started looking into this number after several readers asked about its magnitude.

"What do you think about the administration's plan to spend $200 billion on Katrina relief, which would amount to $400,000 per victim (assuming 500,000 people affected). That could buy (or build) every man, woman and child a pretty nice house, it would seem," wrote Bob from Palo Alto.

The estimate did indeed sound high, so I wanted to see what it included. Would it put New Orleans back the way it was or rebuild some new, utopian New Orleans?

I searched Google and the database Factiva and found hundreds of stories that mentioned the $200 billion cost estimate, but most attributed it to unnamed officials or simply stated it as a fact.

I traced it back to Sept. 6, when Senate Minority Leader Harry Reid of Nevada said the recovery and relief operations "will cost up to and could exceed $150 billion."

I called Reid's office to find out where he got his estimates but didn't get far.

A spokeswoman for Reid said his estimate included "aid to victims, such as food, clothing and shelter" and "about $50 billion for massive public works, rebuilding the economy of the Gulf Coast."

But she couldn't say whether the estimate included rebuilding every home that was destroyed or reinforcing levees for a Category 5 hurricane.

I called Gregg's office to see what was included in his $200 billion estimate, but didn't get much further.

"I think that was a reasonable estimate he gave in terms of how much it would cost the government to rebuild the homes and lives of those affected by Katrina," said Cara Duckworth, press secretary for the Senate Budget Committee. "I can't tell you what he was thinking of in terms of programs. It was a reasonable guess at that time."

"It didn't come from us. We're in the process of determining (an estimate) right now," says Alex Conant, a spokesman for OMB.

Congress has appropriated $62 billion for Katrina relief, "but only $13 billion has been used so far," Conant added. Most of that money has been given to the Federal Emergency Management Agency, with few strings attached.

The bill included $40 billion for Army Corps of Engineer projects, "about 10 times the annual Corps budget for the entire nation, or 16 times the amount the Corps has said it would need to protect New Orleans from a Category 5 hurricane," the Washington Post reported Monday.

The bill included a staggering array of requests, including $400 million for mental health and substance abuse services for Katrina victims, $600 million to rebuild early childhood programs, $25.5 million for sugar cane research, $11 million to replace lost cattle and $10 million for fisheries.

Appropriately, the wish list includes a provision to cover lost Christmas trees.

On Monday, Bill Hoagland, a senior adviser to Senate Majority Leader Bill Frist, R-Tenn., questioned the consensus estimate. "I don't think it was based on any concrete analysis. It may be correct, but it has an equal likelihood of being closer to $100 billion than $200 billion," he said.

Hoagland added up some numbers. The statutory cap on federal supplemental disaster assistance is $26,200 per household. "If 1.1 million households were affected, that's around $30 billion," he said.

"The working assumption, and I think it's overstated, is that there are 400,000 who have lost their jobs and qualify for unemployment assistance. The average (unemployment benefit) is $250 per week. If they all qualify for six months, that's $2.5 billion," he added. Food stamps add another $2.5 billion.

He used the U.S. Department of Agriculture's estimate of farm-related losses: $1 billion.

He added in $30 billion for flood insurance claims, the upper end of the Bush administration's estimate, plus $2 billion in federal tax incentives.

These items add up to almost $70 billion.

The two big numbers he left out were damage to federal property such as weather and military stations, and damage to public infrastructure. When the president declares a disaster area, the federal government picks up 75 to 100 percent of the tab for rebuilding public infrastructure such as roads and bridges.

Although these two are hard to estimate, Hoagland does not think they will bring the total cost to $200 billion.

"It may at the end of the day cost that much, but there is no basis for those numbers just now," he said.

To cross check his numbers, Hoagland looked to Risk Management Solutions, a Newark firm that uses scientific and financial models to estimate disaster costs. Risk Management has estimated total insured losses from Hurricane Katrina at $40 billion to $60 billion.

Hoagland looked at the ratio of insured losses to federal losses in past disasters "and was hard pressed to get it to 1-to-1," he says, suggesting that the cost to the federal government could be less than $100 billion.

Risk Management has estimated "total economic losses" from Katrina at $125 billion. This includes damage to homes, businesses and infrastructure as well as "direct business interruption," says Shannon McKay, the firm's marketing director. It does not include long-term indirect impacts, such as lost tourism or lost wages.

Hoagland fears that if enough people believe the $200 billion estimate "it could become a self-fulfilling prophecy," he said.

"It sounds cruel and heartless (to question post-Katrina spending), but we have to be a little more cautious about throwing these numbers around," he said.